Titanium dioxide is a widely used but increasingly expensive pigment in paints and other coating compositions. In many paint formulations, titanium dioxide represents the single most expensive raw material. A number of techniques and ingredients have been suggested for reducing the amount of titanium dioxide in coating composition formulations while still providing acceptable light scattering or opacity. One such ingredient is EVOQUE™ Pre-Composite Polymer supplied by Dow Chemical Company. EVOQUE products are presently available in four grades (EVOQUE 1140, EVOQUE 1180, EXP-4340 and EXP-4463) that are said to have differing degrees of reactivity towards titanium dioxide. According to its supplier, EVOQUE pre-composite polymer “combines with TiO2 to form a polymer-pigment composite which improves both the wet and dry hiding efficiency of the pigment.” Paints or other coating compositions made from such a composite may attain a given degree of pigment hiding at a somewhat reduced titanium dioxide pigment level, or may attain a somewhat increased degree of pigment hiding at a given titanium dioxide pigment level. However, the potential savings in titanium dioxide raw material costs and the potential benefits in pigment hiding efficiency are offset by the EVOQUE product cost.
A variety of other polymers have been proposed for use with pigments, for example, as pigment dispersing agents. Synthesis of some of these polymers requires expensive starting monomers or complex synthetic schemes. In other instances the polymers have high viscosities, limited pigment dispersing capabilities or other drawbacks. In yet other instances, these dispersants are made by solution polymerization, requiring additional processing to remove solvent(s) prior to use.
From the foregoing, it will be appreciated that what remains needed in the art are improved pigment-containing coating compositions having even lower raw material cost, even greater pigment hiding efficiency, or both lower cost and greater efficiency. Such compositions and components and methods for their manufacture are disclosed and claimed herein.